The watchdog reported that one unidentified prison had been as lax as to remove the “risk of harm” section in the temporary release paperwork in order to “simplify the process”.

Nick Hardwick, the chief inspector of prisons, said current checks were inadequate because they tested inmates’ ability to behave well behind bars rather than in the outside world:

“They are people, on the whole, who are going to be compliant and they've learned how to be good prisoners. But you are not testing whether or not they are going to be good prisoners, you are testing whether or not they are going to be a good citizen and those are two different things.”

He added: ”The public would expect assurance that those processes are properly managed, the risk assessments done properly, and proper attention is given to that. That's a reasonable expectation.“

Reoffending rates for the 13,385 life-sentenced prisoners in England and Wales are low, at only 2 per cent to 5 per cent, but inspectors remain concerned about the serious crimes being committed by inmates out on temporary licenses.

Justice Secretary Chris Grayling ordered a review of the temporary release scheme in July, after a life-sentenced prisoner committed an unprovoked murder on day release.

Today’s report may raise further concerns given the increasing number of life-sentenced criminals in England and Wales. The number has more than trebled in the last five years, rising from 4,000 in 1998 to 13,385 in March 2013.

The length of life-sentences has also increased. In 2001 the average mandatory lifer served 16 years behind bars, while the average is now up to 16 years.

Justice Minister Jeremy Wright said the review would help the prison system “learn lessons and see what changes are necessary”, adding: “We need a process for people to be reintegrated into the community at the end of their sentence, but it needs to be right and it needs to be something the public has confidence in.”